Jet engine aircraft typically employ thrust reversers to supplement landing gear brakes and aerodynamic drag components (e.g., flaps, spoilers, etc.) to slow the aircraft upon landing. A number of thrust reverser designs are known and utilized, including cascade-type thrust reversers, target-type thrust reversers, and pivot door thrust reversers. Each of these thrust reverser designs employs a different type of moveable thrust reverser component, which may be selectively moved between a deployed (landing) and a stowed (in flight) position. When the moveable thrust reverser components are in a deployed (landing) position, the thrust reverser redirects the jet engine's rearward thrust in a generally forward direction. Conversely, when the moveable thrust reverser components are in a stowed (in flight) position, the thrust reverser does not redirect the jet engine's thrust. As an example, one known type of cascade thrust reverser employs a plurality of translating sleeves or cowls (“transcowls”), which covers a series of cascade vanes circumferentially disposed around a jet engine fan case when in the stowed (in flight) position. When the transcowls are moved into the deployed (landing) position, the cascade vanes are exposed and airflow is directed through the exposed cascade veins to produce reward thrust.
Actuators are employed to move the moveable thrust reverser components (e.g., the transcowls) between stowed and deployed positions. For example, a plurality of ballscrew actuators may be coupled to one or more transcowls and cooperate to actuate the transcowls between stowed and deployed positions. A motor (e.g., a dual output power drive unit or PDU) is coupled to each of the ballscrew actuators by way of a plurality of drive mechanisms (e.g., flexible rotatable shafts). The drive mechanisms interconnect the ballscrew actuators to ensure synchronized movement of the transcowls. In response to commands received from a controller, the PDU causes the ballscrew actuators to move the transcowls forward or aft between stowed and deployed positions to cover or uncover the cascade vanes, respectively.
To facilitate thrust reverser maintenance, the actuation system preferably permits the moveable thrust reverser components (e.g., the transcowls) to be manually moved between the stowed position and the deployed position. This may be accomplished by providing at least one ballscrew actuator with a manual drive unit (MDU), which may be configured to receive a specialized tool to permit the manual rotation of the ballscrew actuator. The MDU is preferably provided with a locking mechanism capable of securing the ballscrew actuator in a desired position to maintain the transcowl in any position between the stowed and deployed positions. This locking mechanism may be a bi-directional locking ring assembly comprising, for example, a rack tooth and a spur gear. The rack tooth is configured to translate between a disengaged position that permits spur gear rotation and an engaged position wherein the rack tooth resides between two teeth of the spur gear and physically prevents spur gear rotation.
Known bi-directional locking ring assemblies suffer from at least one disadvantage; i.e., when the apex of the rack tooth contacts the apex or tip of a spur gear tooth, a stable jamming condition occurs. Such a stable jamming condition may prevent the locking mechanism from moving fully into the engaged position and may result in damage to MDU components. Therefore, it should be appreciated that it would be desirable to provide a bi-directional locking ring assembly that substantially eliminates the occurrence of stable jamming conditions. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.